1996 Volume 75 Issue 3 Pages 150-158
Two series of Ni-Mo catalysts were prepared using an impregnation method. In each series Ni/ (Ni+Mo) ratio of the catalysts was varied, while a total met-al loading of Ni and Mo was kept constant (9.9 and 17wt% as MoO3). Sulfiding conditions were varied to give superior catalytic activities. After was sulfiding, model test reactions were carried out to evaluate hydrogenation (HY), hydrocracking (HC) and hydrodesulfurization (HDS) activities of the sulfide catalysts.
The highest HY and HDS activities of the Ni-Mo catalysts were obtained when the Ni/ (Ni+Mo) ratios were 0.3-0.4 and 0.4-0.5 respectively, showing that HY and HDS active sites are different. HC activities decreased with increasing of Ni loading. Similar trends were observed when the total active metal loading was increased from 9.9 to 17wt% as MoO3. While considerable enhancements in HY, HC and HDS activities were observed on the catalysts with high metal loadings.
XPS measurements revealed that atomic ratios of active metal sulfide
{NiS/ (NiS+MoS2)}, which gave the highest HY and HDS activities, were different from those of Ni/ (Ni+Mo). This is mainly due to the different sulfiding behavior between Ni and Mo.
HDS activities increased with increasing of metal sulfiding followed by saturation. However, the catalysts, sulfided at higher temperature, showed lower HDS activities, though metal sulfidings were promoted to some extent. This is probably due to sinter-ing of the active metals, resulting in the decrease of HDS active sites.
